In semiconductor manufacturing apparatuses such as a chemical vapor deposition (CVD) apparatus using plasma, an electromagnetic coupling apparatus using antenna elements is used for generating the plasma.
On the other hand, along with an increase in size of a liquid crystal display or an amorphous solar cell, a semiconductor manufacturing apparatus which uses the plasma to perform each process for processing a substrate having a large area is desired.
Since a frequency of a radio frequency signal used in such a large semiconductor manufacturing apparatus is as high as 10 MHz to 2.5 GHz, a wavelength of the electromagnetic wave emitted from the antenna element is short. Therefore, it is more important to control a plasma density distribution, which affects the uniformity in a process such as film formation, to be uniform.
Under such circumstances, in a plasma CVD apparatus described in Patent Document 1, the use of an antenna for generating a large-area plasma is proposed.
Specifically, an array antenna including a plurality of rod-like antenna elements, each having a surface covered with a dielectric, arranged in a planar manner is used to uniformize a spatial distribution of the electromagnetic wave. Then, the electromagnetic wave is used for generating a large-area plasma.
Patent Document 1: JP 2003-86581 A
Each of the plurality of antenna elements constituting such an antenna array is designed and manufactured to allow a characteristic parameter such as a capacitance or a resistance, which affects an impedance matching state, to provide reflected power of 0% (to provide the best impedance matching state) when radio frequency power is fed.
However, a mechanical manufacturing error is inevitably generated in, for example, the rod-like conductor forming the antenna element, the dielectric (for example, quartz) covering the surface, or a wiring state of a matching circuit for adjusting the impedance matching state. Even when the plasma is generated by using each antenna array configured based on an initial design, the impedance matching state of each of the antenna elements does not become the same as a design value (specifically, the reflected power does not become 0% for all the antenna elements) in many cases due to the error as described above. Therefore, it is necessary to adjust the impedance matching state in advance for each of the antenna elements. Such adjustment of the impedance matching state is necessary not only for the plasma generating apparatus using the array antenna but also for plasma generating apparatuses using other configurations.